It is well known that solid titanium catalyst component with magnesium, titanium, halogen and electron donor as basic compositions can be used in the polymerization of olefin CH2═CHR, especially in the polymerization of alpha-olefins having 3 or more carbon atoms, higher isotactic polymer can be obtained in higher yield. An electron donor compound is one of indispensable compositions of catalyst component, and with the development of internal donor compound, polyolefin catalyst is continuously renovated. At present, a large amount of various electron donor compounds have been disclosed, for instance, polycarboxylic acids, monocarboxylic esters or polycarboxylic esters, anhydrides, ketones, monoethers or polyethers, alcohols, amines, and their derivatives, among of which aromatic dicarboxylic ester, such as di-n-butyl phthalate or diisobutyl phthalate (cf. U.S. Pat. No. 4,784,983), is common.
In recent years, the use of other compounds as electron donor compounds of catalyst for polymerization of olefins have been tried, for examples, U.S. Pat. No. 4,971,937 and EP 0728769 disclosed a catalyst component for polymerization of olefins, which used special 1,3-diether compounds containing two ether groups, such as 2-isoamyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane and 9,9-bis(methoxymethyl)fluorene and the like as electron donor.
Lately, a special type of aliphatic dicarboxylic ester compounds, such as succinate, malonate, glutarate and the like had been disclosed (cf. WO98/56830, WO98/56834, WO01/57099, WO01/63231 and WO00/55215), and the use of said electron donor compound not only enhanced the activity of catalyst but also substantially broadened the distribution of the molecular weight of the propylene polymer obtained.
However, above-mentioned olefin polymerization catalysts prepared utilizing disclosed aromatic dicarboxylic ester compound, 1,3-diether compound containing two ether groups and aliphatic dicarboxylic ester compound exist certain defects in actual use. For instance, the catalytic activity of the catalyst with aromatic dicarboxylic ester compound is low, and the distribution of the molecular weight of the polymer obtained is narrow; although the catalyst with 1,3-diether compound has high catalytic activity and good hydrogen response, the distribution of the molecular weight of the polymer obtained is narrow, and this is disadvantageous in the development of different grades of polymers; and the catalytic activity of the catalyst with aliphatic dicarboxylic ester compound disclosed recently is still some low, and when external donor compound is not used, the isotacticity of the polymer obtained is lower.
The inventors have surprisingly found that an olefin polymerization catalyst with excellent general properties can be obtained by using a polyol ester compound with a special structure as electron donor. When the catalyst is used in the polymerization of propylene, satisfactory polymerization yield can be obtained, and the stereo-direction of the polymer is very high. Even if an external donor is not used, relatively high isotactic polymer can still be obtained. Meanwhile, the hydrogen response of the catalyst is excellent, and the distribution of the molecular weight of the polymer obtained is relatively wide, and these properties are desirable in the development of different grades of polymers. In addition, when the catalyst is used in the copolymerization of olefins, especially in the copolymerization of ethylene and propylene, less gel content can be achieved, therefore, it has better copolymerization property.